Controlling handover

ABSTRACT

Apparatus and method for controlling handover are disclosed. The solution comprises obtaining information on slices supported by surrounding base stations; obtaining information on overloaded slices used by the surrounding base stations; receiving a measurement report from a user terminal utilizing slices in communication; determining based on the measurement report that a handover is needed for the user terminal; selecting from the surrounding base stations a target base station for handover based on the measurement report, slices supported by the base stations and the information on overloaded slices.

TECHNICAL FIELD

The exemplary and non-limiting embodiments of the invention relategenerally to communications.

BACKGROUND

Wireless telecommunication systems are under constant development. Thereis a constant need for higher data rates and high quality of service.Reliability requirements are constantly rising and ways and means toensure reliable connections and data traffic while keeping transmissiondelays minimal are constantly under development.

In communication systems, and communication systems supporting multipleaccess nodes or base stations in particular, handover is one of the keyprocedures carried out for mobility while in connected. In many systems,handover procedure of a user terminal is initiated based on themeasurement report received from user terminal when a reference signalreceived power level from a nearby node is better than the referencesignal received power level from the serving node. Source node initiateshandover request to target node and upon successful handover, thecommunication link or links are transferred to the target node.

Developing networks enable new services to customers. One suggestedservice is Network Slicing, which enables offering connectivity, qualityof service and data processing solutions tailored to specific customers'requirements. A network slice is a logical end-to-end virtual networkthat can be dynamically created and that provides specific capabilitiesand characteristics.

User terminals may utilise one or more slices in communication. Toensure smooth handovers and efficient mobility between the nodes slicesshould be taken into account.

BRIEF DESCRIPTION

According to an aspect of the present invention, there is provided anapparatus in a communication system, the apparatus comprising at leastone processor; at least one memory including computer program code; theat least one memory and the computer program code configured to, withthe at least one processor, cause the apparatus at least to perform:obtain information on slices supported by surrounding base stations;obtain information on overloaded slices used by the surrounding basestations; receive a measurement report from a user terminal utilizingslices in communication; determine based on the measurement report thata handover is needed for the user terminal; select from the surroundingbase stations a target base station for handover based on themeasurement report, slices supported by the base stations and theinformation on overloaded slices, wherein if in the surrounding basestations more than one is acceptable based on the measurement report,select as a target base station the base station offering maximum numberof non-overloaded slices required by the user terminal.

According to an aspect of the present invention, there is provided anapparatus in a communication system, the apparatus comprising at leastone processor; at least one memory including computer program code; theat least one memory and the computer program code configured to, withthe at least one processor, cause the apparatus at least to perform:determine the resource availability of the slices the apparatus issupporting; indicate to surrounding base stations if one or more sliceshave load exceeding a given first overload limit; and indicate tosurrounding base stations if one or more slices that previously had loadexceeding a given overload limit has load fallen below a given secondoverload limit.

According to an aspect of the present invention, there is provided amethod in a communication system, comprising: obtaining information onslices supported by surrounding base stations; obtaining information onoverloaded slices used by the surrounding base stations; receiving ameasurement report from a user terminal utilizing slices incommunication; determining based on the measurement report that ahandover is needed for the user terminal; selecting from the surroundingbase stations a target base station for handover based on themeasurement report, slices supported by the base stations and theinformation on overloaded slices, wherein if in the surrounding basestations more than one is acceptable based on the measurement report,select as a target base station the base station offering maximum numberof non-overloaded slices required by the user terminal.

According to an aspect of the present invention, there is provided amethod in a communication system, comprising: determining the resourceavailability of supported slices; indicating to surrounding basestations if one or more slices have load exceeding a given firstoverload limit; and indicating to surrounding base stations if one ormore slices that previously had load exceeding a given overload limithas load fallen below a given second overload limit.

According to an aspect of the present invention, there is provided acomputer program comprising instructions for causing an apparatus of acommunication system to perform at least the following: obtaininginformation on slices supported by surrounding base stations; obtaininginformation on overloaded slices used by the surrounding base stations;receiving a measurement report from a user terminal utilizing slices incommunication; determining based on the measurement report that ahandover is needed for the user terminal; selecting from the surroundingbase stations a target base station for handover based on themeasurement report, slices supported by the base stations and theinformation on overloaded slices, wherein if in the surrounding basestations more than one is acceptable based on the measurement report,select as a target base station the base station offering maximum numberof non-overloaded slices required by the user terminal.

According to an aspect of the present invention, there is provided acomputer program comprising instructions for causing an apparatus of acommunication system to perform at least the following: determining theresource availability of supported slices; indicating to surroundingbase stations if one or more slices have load exceeding a given firstoverload limit; and indicating to surrounding base stations if one ormore slices that previously had load exceeding a given overload limithas load fallen below a given second overload limit.

The scope of protection sought for various embodiments of the inventionis set out by the independent claims.

The embodiments and or examples and features, if any, described in thisspecification that do not fall under the scope of the independent claimsare to be interpreted as examples useful for understanding variousembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail bymeans of preferred embodiments with reference to the accompanyingdrawings, in which

FIG. 1 illustrates an example of a communication environment where someembodiments of the invention may be applied;

FIG. 2 is a signalling chart illustrating an embodiment;

FIG. 3 is a flowchart illustrating an embodiment;

FIG. 4 is a signalling chart illustrating an embodiment;

FIG. 5 is a flowchart illustrating an embodiment;

FIGS. 6 and 7 illustrate examples of connections between base stations;and

FIG. 8 illustrates an example of an apparatus employing some embodimentsof the invention.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

In the following, different exemplifying embodiments will be describedusing, as an example an access architecture to which the embodiments maybe applied, a radio access architecture based on long term evolutionadvanced (LTE Advanced, LTE-A), enhanced LTE (eLTE), or new radio (NR,5G), without restricting the embodiments to such an architecture,however. It is obvious for a person skilled in the art that theembodiments may also be applied to other kinds of communicationsnetworks having suitable means by adjusting parameters and proceduresappropriately. Some examples of other options for suitable systems maybe the universal mobile telecommunications system (UMTS) radio accessnetwork (UTRAN or E-UTRAN), long term evolution (LTE, the same asE-UTRA), wireless local area network (WLAN or WiFi), worldwideinteroperability for microwave access (WiMAX), or any combinationthereof.

FIG. 1 depicts examples of simplified system architectures only showingsome elements and functional entities, all being logical units, whoseimplementation may differ from what is shown. The connections shown inFIG. 1 are logical connections; the actual physical connections may bedifferent. It is apparent to a person skilled in the art that the systemtypically comprises also other functions and structures than those shownin FIG. 1.

The embodiments are not, however, restricted to the system given as anexample but a person skilled in the art may apply the solution to othercommunication systems provided with necessary properties.

The example of FIG. 1 shows a part of an exemplifying radio accessnetwork.

FIG. 1 shows user devices 100 and 102 configured to be in a wirelessconnection on one or more communication channels in a cell with anaccess node (such as (e/g)NodeB) 104 providing the cell. The physicallink from a user device to a (e/g)NodeB is called uplink or reverse linkand the physical link from the (e/g)NodeB to the user device is calleddownlink or forward link. It should be appreciated that (e/g)NodeBs ortheir functionalities may be implemented by using any node, host, serveror access point etc. entity suitable for such a usage.

A communications system typically comprises more than one (e/g)NodeB inwhich case the (e/g)NodeBs may also be configured to communicate withone another over links, wired or wireless, designed for the purpose.These links may be used for data and signaling purposes. The (e/g)NodeBis a computing device configured to control the radio resources ofcommunication system it is coupled to. The (e/g)NodeB may also bereferred to as a base station, an access point or any other type ofinterfacing device including a relay station capable of operating in awireless environment. The (e/g)NodeB includes or is coupled totransceivers. From the transceivers of the (e/g)NodeB, a connection isprovided to an antenna unit that establishes bi-directional radio linksto user devices. The antenna unit may comprise a plurality of antennasor antenna elements. The (e/g)NodeB is further connected to core network106 (CN or next generation core NGC). Depending on the system, thecounterpart on the CN side can be a serving gateway (S-GW, routing andforwarding user data packets), packet data network gateway (P-GW), forproviding connectivity of user devices (UEs) to external packet datanetworks, or mobile management entity (MME), User Plane Function (UPF),etc.

The user device (also called UE, user equipment, user terminal, terminaldevice, etc.) illustrates one type of an apparatus to which resources onthe air interface are allocated and assigned, and thus any featuredescribed herein with a user device may be implemented with acorresponding apparatus, such as a relay node. An example of such arelay node is a layer 3 relay (self-backhauling relay) towards the basestation.

The user device typically refers to a portable computing device thatincludes wireless mobile communication devices operating with or withouta subscriber identification module (SIM), including, but not limited to,the following types of devices: a mobile station (mobile phone),smartphone, personal digital assistant (PDA), handset, device using awireless modem (alarm or measurement device, etc.), laptop and/or touchscreen computer, tablet, game console, notebook, and multimedia device.It should be appreciated that a user device may also be a nearlyexclusive uplink only device, of which an example is a camera or videocamera loading images or video clips to a network. A user device mayalso be a device having capability to operate in Internet of Things(IoT) network which is a scenario in which objects are provided with theability to transfer data over a network without requiring human-to-humanor human-to-computer interaction. One technology in the above networkmay be denoted as narrowband Internet of Things (NB-Iot). The userdevice may also be a device having capability to operate utilizingenhanced machine-type communication (eMTC). The user device may alsoutilize cloud. In some applications, a user device may comprise a smallportable device with radio parts (such as a watch, earphones oreyeglasses) and the computation is carried out in the cloud. The userdevice (or in some embodiments a layer 3 relay node) is configured toperform one or more of user equipment functionalities. The user devicemay also be called a subscriber unit, mobile station, remote terminal,access terminal, user terminal or user equipment (UE) just to mentionbut a few names or apparatuses.

Various techniques described herein may also be applied to acyber-physical system (CPS) (a system of collaborating computationalelements controlling physical entities). CPS may enable theimplementation and exploitation of massive amounts of interconnected,ICT, devices (sensors, actuators, processors microcontrollers, etc.)embedded in physical objects at different locations. Mobile cyberphysical systems, in which the physical system in question has inherentmobility, are a subcategory of cyber-physical systems. Examples ofmobile physical systems include mobile robotics and electronicstransported by humans or animals.

Additionally, although the apparatuses have been depicted as singleentities, different units, processors and/or memory units (not all shownin FIG. 1) may be implemented.

5G enables using multiple input-multiple output (MIMO) antennas, perhapsmore base stations or nodes than the LTE (a so-called small cellconcept), including macro sites operating in co-operation with smallerstations and employing a variety of radio technologies depending onservice needs, use cases and/or spectrum available. 5G mobilecommunications support a wide range of use cases and relatedapplications including video streaming, augmented reality, differentways of data sharing and various forms of machine type applications(such as (massive) machine-type communications (mMTC), includingvehicular safety, different sensors and real-time control. 5G isexpected to have multiple radio interfaces, namely below 6 GHz, andmmWave, and also being integrable with existing legacy radio accesstechnologies, such as the LTE. Integration with the LTE may beimplemented, at least in the early phase, as a system, where macrocoverage is provided by the LTE and 5G radio interface access comes fromsmall cells by aggregation to the LTE. In other words, 5G is planned tosupport both inter-RAT operability (such as LTE-5G) and inter-RIoperability (inter-radio interface operability, such as below 6GHz-cmWave, above 6 GHz-mmWave). As mentioned, one of the conceptsconsidered to be used in 5G networks is network slicing in whichmultiple independent and dedicated virtual sub-networks (networkinstances) may be created within the same infrastructure.

The current architecture in LTE networks is fully distributed in theradio and fully centralized in the core network. The low latencyapplications and services in 5G require to bring the content close tothe radio which leads to local break out and mobile edge computing,(MEC). 5G enables analytics and knowledge generation to occur at thesource of the data. This approach requires leveraging resources that maynot be continuously connected to a network such as laptops, smartphones,tablets and sensors. Mobile edge computing provides a distributedcomputing environment for application and service hosting. It also hasthe ability to store and process content in close proximity to cellularsubscribers for faster response time. Edge computing covers a wide rangeof technologies such as wireless sensor networks, mobile dataacquisition, mobile signature analysis, cooperative distributedpeer-to-peer ad hoc networking and processing also classifiable as localcloud/fog computing and grid/mesh computing, dew computing, mobile edgecomputing, cloudlet, distributed data storage and retrieval, autonomicself-healing networks, remote cloud services, augmented and virtualreality, data caching, Internet of Things (massive connectivity and/orlatency critical), critical communications (autonomous vehicles, trafficsafety, real-time analytics, time-critical control, healthcareapplications).

The communication system is also able to communicate with othernetworks, such as a public switched telephone network or the Internet112, or utilize services provided by them. The communication network mayalso be able to support the usage of cloud services, for example atleast part of core network operations may be carried out as a cloudservice (this is depicted in FIG. 1 by “cloud” 114). The communicationsystem may also comprise a central control entity, or a like, providingfacilities for networks of different operators to cooperate for examplein spectrum sharing.

Edge cloud may be brought into radio access network (RAN) by utilizingnetwork function virtualization (NVF) and software defined networking(SDN). Using edge cloud may mean access node operations to be carriedout, at least partly, in a server, host or node operationally coupled toa remote radio head or base station comprising radio parts. It is alsopossible that node operations will be distributed among a plurality ofservers, nodes or hosts. Application of cloudRAN architecture enablesRAN real time functions being carried out at the RAN side (in adistributed unit, DU 104) and non-real time functions being carried outin a centralized manner (in a centralized unit, CU 108).

It should also be understood that the distribution of labor between corenetwork operations and base station operations may differ from that ofthe LTE or even be non-existent. Some other technology advancementsprobably to be used are Big Data and all-IP, which may change the waynetworks are being constructed and managed. 5G (or new radio, NR)networks are being designed to support multiple hierarchies, where MECservers can be placed between the core and the base station or nodeB(gNB). It should be appreciated that MEC can be applied in 4G networksas well.

In an embodiment, 5G may also utilize satellite communication to enhanceor complement the coverage of 5G service, for example by providingbackhauling. Possible use cases are providing service continuity formachine-to-machine (M2M) or Internet of Things (IoT) devices or forpassengers on board of vehicles, or ensuring service availability forcritical communications, and future railway/maritime/aeronauticalcommunications. Satellite communication may utilize geostationary earthorbit (GEO) satellite systems, but also low earth orbit (LEO) satellitesystems, in particular mega-constellations (systems in which hundreds of(nano)satellites are deployed). Each satellite 110 in themega-constellation may cover several satellite-enabled network entitiesthat create on-ground cells. The on-ground cells may be created throughan on-ground relay node 104 or by a gNB located on-ground or in asatellite.

It is obvious for a person skilled in the art that the depicted systemis only an example of a part of a radio access system and in practice,the system may comprise a plurality of (e/g)NodeBs, the user device mayhave an access to a plurality of radio cells and the system may comprisealso other apparatuses, such as physical layer relay nodes or othernetwork elements, etc. At least one of the (e/g)NodeBs may be aHome(e/g)nodeB. Additionally, in a geographical area of a radiocommunication system a plurality of different kinds of radio cells aswell as a plurality of radio cells may be provided. Radio cells may bemacro cells (or umbrella cells) which are large cells, usually having adiameter of up to tens of kilometers, or smaller cells such as micro-,femto- or picocells. The (e/g)NodeBs of FIG. 1 may provide any kind ofthese cells. A cellular radio system may be implemented as a multilayernetwork including several kinds of cells. Typically, in multilayernetworks, one access node provides one kind of a cell or cells, and thusa plurality of (e/g)NodeBs are required to provide such a networkstructure.

For fulfilling the need for improving the deployment and performance ofcommunication systems, the concept of “plug-and-play” (e/g)NodeBs hasbeen introduced. Typically, a network which is able to use“plug-and-play” (e/g)Node Bs, includes, in addition to Home (e/g)NodeBs(H(e/g)nodeBs), a home node B gateway, or HNB-GW (not shown in FIG. 1).A HNB Gateway (HNB-GW), which is typically installed within anoperator's network may aggregate traffic from a large number of HNBsback to a core network.

As mentioned, radio access network may be split into two logicalentities called Central Unit (CU) and Distributed Unit (DU). In priorart, both CU and DU supplied by the same vendor. Thus, they are designedtogether and interworking between the units is easy. The interfacebetween CU and DU is currently being standardized by 3GPP and it isdenoted F1 interface. Therefore, in the future the network operators mayhave the flexibility to choose different vendors for CU and DU.Different vendors can provide different failure and recoverycharacteristics for the units. If the failure and recovery scenarios ofthe units are not handled in a coordinated manner, it will result ininconsistent states in the CU and DU (which may lead to subsequent callfailures, for example). Thus there is a need to enable the CU and DUfrom different vendors to coordinate operation to handle failureconditions and recovery, taking into account the potential differencesin resiliency capabilities between the CU and DU.

As mentioned above, network slicing is a concept where network resourcesof an end-to-end connection between a user terminal and another endpoint in a public land mobile network (PLMN) are sliced. Similar networkslicing may be employed also in private networks. A network slice may beunderstood as a logical end-to-end network that can be dynamicallycreated and/or modified. The network(s) between the end devices may allbe sliced from one end device to the other end device, the slices thusforming logical pipelines within the network(s). User terminal mayaccess a slice over a radio interface. Each pipeline/slice may serve aparticular service type. So far, three different network slice/servicetypes have ben been standardized: eMBB (slice suitable for the handlingof 5G enhanced Mobile Broadband), URLLC (slice suitable for the handlingof Ultra-Reliable Low Latency Communications) and MIoT (slice suitablefor the handling of massive Internet of Things). Communications ServiceProviders (CSPs) are able to define additional network slice/servicetypes if needed. A given user terminal may access to multiple slicesover the same Access Network (over the same radio interface, forexample).

Thus, network slicing enables a communications service provider toprovide dedicated virtual networks over a common network infrastructure.The different virtual or logical networks may be designed to providedifferent networking characteristics such as different qualities ofservice (QoS). For example, the virtual networks may be customized tomeet specific needs of various applications, services, devices,customers and/or operators.

In a system where network slicing is utilized, a single physical networkor a group of networks is sliced into multiple virtual networks (slices)that can support different radio access networks (RANs) or differentservice types running across a single RAN. The network slicing may beused to partition a core network of a cellular communication system suchas a 5G system, but it may also be implemented in the RAN such as theWLAN.

Each network slice may be optimized to provide resources and networktopology for the specific service and traffic that will use the slice.Network resources may be allocated according to requirements in terms ofmobility, capacity, connectivity and coverage such that particulardemands of each use case will be met. Physical network components orresources may be shared across different network slices.

The slices supported by nearby base stations or access nodes may vary.In the existing mobility procedure, the handover of a user terminal froma source base station to a target base station is initiated only basedon the measurement report received from the user terminal. However,slice aware admission and load status of the target base station is notbeing evaluated by the source base station before the initiation ofhandover request. Hence there is a possibility of a rejection ofhandover by the target base station based on slice or resourceavailability.

In an embodiment of the invention, selection of handover target basestation is performed not only based on the user terminal measurementreport but also for slice availability and congestion status for thespecific slice. This will help to find the best suitable neighbour cellbased on the slices.

FIG. 2 is a signalling chart illustrating an embodiment, FIG. 3 is aflowchart illustrating the operation of a source gNB and FIG. 4 is aflowchart illustrating the operation of a a gNB in general in anembodiment.

FIG. 2 illustrates an example where a user terminal 100 is connected toa gNB1 200. The user terminal utilises slices in communication. In thissimplified example there are two nearby gNBs, gNB2 202 and gNB3 204.

In phase 206, the gNBs are configured to indicate to other gNBs slicessupported by the gNBs. In an embodiment, the gNBs obtain the informationfrom NG-RAN Node configuration Update-message.

In phase 208, the gNBs are configured to determine current load perslice.

The gNBs are configured to determine indicate to other gNBs if there areslices that have overload, i.e. lack of resources to receive newconnections. In this example, gNB2 202 has overload on a slice. The gNB2indicates 210 the overload to gNB1 200 and gNB3 204.

The user terminal 100 transmits 212 a measurement report to the gNB1200. The measurement report may comprise Reference Signal ReceivedPower, RSRP, Reference Signal Received Quality, RSRQ and/orSignal-to-Interference-plus-Noise Ratio, SINR, measurements performed bythe user terminal regarding the source gNB1 and nearby gNBs.

Based on the measurement report the source gNB1 200 determines in thisexample that a handover is needed for the user terminal 100.

In phase 214, the gNB1 200 is configured to determine the target gNB forthe handover. In an embodiment, the gNB1 200 is configured to selectfrom the surrounding base stations a target base station for handoverbased on the measurement report, slices supported by the base stationsand the information on overloaded slices.

In this example, the source gNB1 selects gNB3 as the target gNB becausegNB2 has indicated that it had overload. The source gNB1 transmits ahandover request message 216 to the gNB3.

Let us study an embodiment a bit closer referring to FIG. 3. FIG. 3illustrates examples of the operation of an apparatus or a networkelement configured to control handover of user terminals In anembodiment, FIG. 4 illustrates the operation of gNB or a part of an gNB.

In step 300 of FIG. 3, the apparatus is configured to obtain informationon slices supported by surrounding base stations. In an embodiment, theapparatus obtains the information from NG-RAN Node configurationUpdate-message.

In step 302 of FIG. 3, the apparatus is configured to obtain informationon overloaded slices used by the surrounding base stations. In anembodiment, the apparatus may receive messages from surrounding basestations via Xn interface. In an embodiment, the apparatus may receivemessages from surrounding base stations via Core Access and MobilityManagement Function, AMF, of the communication system, which is acontrol plane core connector for radio access network and can be seenfrom this perspective as the 5G version of Mobility Management Entity,MME, in LTE.

In step 304 of FIG. 3, the apparatus is configured to receive ameasurement report from a user terminal utilizing slices incommunication. As mentioned, the measurement report may comprise RSRP,RSRQ and/or SINR, measurements performed by the user terminal regardingthe source gNB1 and nearby gNBs, for example.

In step 306 of FIG. 3, the apparatus is configured to determine, basedon the measurement report, that a handover is needed for the userterminal. The signal quality reported from a surrounding gNB may bebetter than that the source gNB may offer, for example.

In step 308 of FIG. 3, the apparatus is configured to select from thesurrounding base stations a target base station for handover based onthe measurement report, slices supported by the base stations and theinformation on overloaded slices.

As a numeric example, referring to FIG. 2, RSRP of gNB2 may be −44 dBand RSRP of gNB3 may be −60 dB. However, gNB2 has reported eMMB sliceload to be over a given overload limit, for example 90%, whereas gNB3has not reported overload. In this example, gNB1 may select gNB3 as thetarget gNB for handover, as it has resources available whereas gNB2 hasnot, in spite of gNB2 having better RSRP than gNB3. The trade-offbetween RSRP and load status can be decided based on the history of RSRPrange required for specific slice, for example.

In an embodiment, if in the surrounding base stations only one isacceptable based on the measurement report, that base station may beselected as the target base station.

In an embodiment, if in the surrounding base stations more than one isacceptable based on the measurement report, the source gNB may select asa target base station the base station offering maximum number ofnon-overloaded slices required by the user terminal.

In an embodiment, the source gNB may receive from surrounding basestations indication of slices supported by the base stations that haveload exceeding a given first overload limit.

In an embodiment, the source gNB may receive from surrounding basestations indication of slices that previously had load exceeding a givenfirst overload limit have load reduced below a given second overloadlimit. This is illustrated in FIG. 4, which may be a continuation to theexample of FIG. 2, where gNB2 reported a slice having overload. In phase400, the gNBs are configured to determine current load per slice. Inthis example, gNB2 202 determines that the load of the given slice whichpreviously had overload, has reduced below a given limit. Now gNB2indicates 402 to other gNBs, that the slice has no longer a overloadsituation.

FIG. 5 is a flowchart illustrating an embodiment. FIG. 5 illustratesexamples of the operation of an apparatus or a network element. In anembodiment, FIG. 5 illustrates the operation of gNB or a part of an gNB.

In step 500 of FIG. 5, the apparatus is configured to determine theresource availability of the slices the apparatus is supporting.

In step 502 of FIG. 5, the apparatus is configured to determine if oneor more slices have load exceeding a given overload limit.

If so, the apparatus is configured to, in step 504, indicate tosurrounding base stations that one or more slices have load exceeding agiven overload limit.

In step 506 of FIG. 5, the apparatus is configured to determine if oneor more slices that previously had load exceeding a given overload limithave load fallen below a given second overload limit.

If so, the apparatus is configured to, in step 508, indicate tosurrounding base stations that one or more slices that previously hadload exceeding a given overload limit have load fallen below a givensecond overload limit.

In an embodiment, the first and second overload limits are received fromthe communication system. In an embodiment, the operator of thecommunication system can define the limits for the slice resource interms of bandwidth usage, number of Packet Data Unit, PDU, sessions,number of flows or even processor/buffer memory usage, for example. Loadexceeding the first overload limit denotes that a slice has an overload,and load dropping below the second overload limit denotes the end ofoverload. Typically, to avoid frequent indication messages, the firstoverload limit is larger than the second overload limit. For example,the first overload limit may be 90% and the second overload limit may be80%. These non-limiting numerical values are for illustrative purposesonly.

The procedure described in FIG. 5 may be continuous or performed atgiven time intervals. As soon as overload or end of overload is detectedit may be indicated to surrounding gNBs.

FIG. 6 illustrates an embodiment. FIG. 6 shows four gNBs 100, 200, 202,600. The gNB2 202 determines load of supported slices. In the example ofFIG. 6, gNB2 202 utilises an Xn control message to indicate overload orend of overload. The Xn control message will be broadcasted to all theXn neighbors.

FIG. 7 illustrates another embodiment. FIG. 7 shows six gNBs 100, 200,202, 600, 702 and 704. Part of the gNBS are connected to gNB 202 with Xninterface, part of the gNBs are connected to Core Access and MobilityManagement Function, AMF 700, of the communication system. The gNB2 202determines load of supported slices. In the example of FIG. 7, gNB2broadcasts Xn control message to all the Xn neighbors 100, 200, 202, 600and to AMF 700. The AMF 700 can in turn broadcast the message to all thegNBs 702, 704 in the (slice)registration area.

FIG. 8 illustrates an embodiment. The figure illustrates a simplifiedexample of an apparatus applying embodiments of the invention. In someembodiments, the apparatus may be a gNB, or any other entity or networkelement of the communication system provided that the necessary inputsare available and required interfaces exists to transmit and receiverequired information.

It should be understood that the apparatus is depicted herein as anexample illustrating some embodiments. It is apparent to a personskilled in the art that the apparatus may also comprise other functionsand/or structures and not all described functions and structures arerequired. Although the apparatus has been depicted as one entity,different modules and memory may be implemented in one or more physicalor logical entities.

The apparatus 800 of the example includes a control circuitry 802configured to control at least part of the operation of the apparatus.The control circuitry may be realized as a processor or more than oneprocessors, for example.

The apparatus may comprise a memory 804 for storing data. Furthermorethe memory may store software 806 executable by the control circuitry802. The memory may be integrated in the control circuitry.

The apparatus may comprise one or more interface circuitries 808, 810.The interface(s) may connect the apparatus to other network elements ofthe communication system. The interface(s) may provide a wired orwireless connection to the communication system. The interface(s) may beoperationally connected to the control circuitry 802.

The software 806 may comprise a computer program comprising program codemeans adapted to cause the control circuitry 802 of the apparatus toperform the embodiments described above and in the claims.

In an embodiment, the apparatus comprises at least one processor orcontrol circuitry 802 and at least one memory 804 including a computerprogram code 806, wherein the at least one memory and the computerprogram code are configured, with the at least one processor, to causethe apparatus to carry out the functionalities of the apparatus 800according to any one of the embodiments of described above and in theclaims.

According to an aspect, when the at least one processor or controlcircuitry 802 executes the computer program code, the computer programcode causes the apparatus to carry out the functionalities according toany one of the embodiments described above and in the claims.

According to another embodiment, the apparatus comprises the at leastone processor or control circuitry 802 and at least one memory 804including a computer program code 806, wherein the at least oneprocessor or control circuitry 802 and the computer program code 806perform the at least some of the functionalities of the apparatus 800according to any one of the embodiments described above and in theclaims. Accordingly, the at least one processor or control circuitry802, the memory, and the computer program code form processing means forcarrying out some embodiments of the present invention in the apparatus800.

In an embodiment, the apparatus comprises means for obtaininginformation on slices supported by surrounding base stations; means forobtaining information on overloaded slices used by the surrounding basestations; means for receiving a measurement report from a user terminalutilizing slices in communication; means for determining based on themeasurement report that a handover is needed for the user terminal andmeans for selecting from the surrounding base stations a target basestation for handover based on the measurement report, slices supportedby the base stations and the information on overloaded slices.

In an embodiment, the apparatus comprises means for determining theresource availability of the slices the apparatus is supporting, meansfor indicating to surrounding base stations if one or more slices haveload exceeding a given first overload limit; and means for indicating tosurrounding base stations if one or more slices that previously had loadexceeding a given overload limit has load fallen below a given secondoverload limit.

In an embodiment, the processes or methods described in above figuresmay also be carried out in the form of one or more computer processesdefined by one or more computer program. A separate computer program maybe provided in one or more apparatuses that execute functions of theprocesses described in connection with the figures. The computerprogram(s) may be in source code form, object code form, or in someintermediate form, and it may be stored in some sort of carrier, whichmay be any entity or device capable of carrying the program. Suchcarriers include transitory and/or non-transitory computer media, e.g. arecord medium, computer memory, read-only memory, electrical carriersignal, telecommunications signal, and software distribution package.Depending on the processing power needed, the computer program may beexecuted in a single electronic digital processing unit or it may bedistributed amongst a number of processing units.

The steps and related functions described in the above and attachedfigures are in no absolute chronological order, and some of the stepsmay be performed simultaneously or in an order differing from the givenone. Other functions can also be executed between the steps or withinthe steps. Some of the steps can also be left out or replaced with acorresponding step.

The apparatuses or controllers able to perform the above-described stepsmay be implemented as an electronic digital computer, which may comprisea working memory (RAM), a central processing unit (CPU), and a systemclock. The CPU may comprise a set of registers, an arithmetic logicunit, and a controller. The controller is controlled by a sequence ofprogram instructions transferred to the CPU from the RAM. The controllermay contain a number of microinstructions for basic operations. Theimplementation of microinstructions may vary depending on the CPUdesign. The program instructions may be coded by a programming language,which may be a high-level programming language, such as C, Java, etc.,or a low-level programming language, such as a machine language, or anassembler. The electronic digital computer may also have an operatingsystem, which may provide system services to a computer program writtenwith the program instructions.

As used in this application, the term ‘circuitry’ refers to all of thefollowing: (a) hardware-only circuit implementations, such asimplementations in only analog and/or digital circuitry, and (b)combinations of circuits and software (and/or firmware), such as (asapplicable): (i) a combination of processor(s) or (ii) portions ofprocessor(s)/software including digital signal processor(s), software,and memory(ies) that work together to cause an apparatus to performvarious functions, and (c) circuits, such as a microprocessor(s) or aportion of a microprocessor(s), that require software or firmware foroperation, even if the software or firmware is not physically present.

This definition of ‘circuitry’ applies to all uses of this term in thisapplication. As a further example, as used in this application, the term‘circuitry’ would also cover an implementation of merely a processor (ormultiple processors) or a portion of a processor and its (or their)accompanying software and/or firmware. The term ‘circuitry’ would alsocover, for example and if applicable to the particular element, abaseband integrated circuit or applications processor integrated circuitfor a mobile phone or a similar integrated circuit in a server, acellular network device, or another network device.

The computer program may be in source code form, object code form, or insome intermediate form, and it may be stored in some sort of carrier,which may be any entity or device capable of carrying the program. Suchcarriers include a record medium, computer memory, read-only memory, anda software distribution package, for example. Depending on theprocessing power needed, the computer program may be executed in asingle electronic digital computer or it may be distributed amongst anumber of computers.

The apparatus may also be implemented as one or more integratedcircuits, such as application-specific integrated circuits, ASICs. Otherhardware embodiments are also feasible, such as a circuit built ofseparate logic components. A hybrid of these different implementationsis also feasible. When selecting the method of implementation, a personskilled in the art will consider the requirements set for the size andpower consumption of the apparatus, the necessary processing capacity,production costs, and production volumes, for example.

It will be obvious to a person skilled in the art that, as thetechnology advances, the inventive concept can be implemented in variousways. The invention and its embodiments are not limited to the examplesdescribed above but may vary within the scope of the claims.

1. An apparatus in a communication system, the apparatus comprising: atleast one processor; at least one memory including computer programcode; the at least one memory and the computer program code configuredto, with the at least one processor, cause the apparatus at least to:obtain information on slices supported by surrounding base stations;obtain information on overloaded slices used by the surrounding basestations; receive a measurement report from a user terminal utilizingslices in communication; determine based on the measurement report thata handover is needed for the user terminal; select from the surroundingbase stations a target base station for handover based on themeasurement report, slices supported by the base stations and theinformation on overloaded slices, wherein if in the surrounding basestations more than one is acceptable based on the measurement report,select as a target base station the base station offering maximum numberof non-overloaded slices required by the user terminal.
 2. The apparatusof claim 1, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatusfurther to: receive from surrounding base stations indication of slicessupported by the base stations that have load exceeding a given firstoverload limit.
 3. The apparatus of claim 2, the at least one memory andthe computer program code configured to, with the at least oneprocessor, cause the apparatus further to: receive from surrounding basestations indication of slices that previously had load exceeding a givenfirst overload limit have load reduced below a given second overloadlimit.
 4. The apparatus of claim 1, the at least one memory and thecomputer program code configured to, with the at least one processor,cause the apparatus further to: if in the surrounding base stations onlyone is acceptable based on the measurement report, select that basestation as the target base station.
 5. An apparatus in a communicationsystem, the apparatus comprising: at least one processor; at least onememory including computer program code; the at least one memory and thecomputer program code configured to, with the at least one processor,cause the apparatus at least to: determine the resource availability ofthe slices the apparatus is supporting; indicate to surrounding basestations if one or more slices have load exceeding a given firstoverload limit; and indicate to surrounding base stations if one or moreslices that previously had load exceeding a given overload limit hasload fallen below a given second overload limit.
 6. The apparatus ofclaim 5, the at least one memory and the computer program codeconfigured to, with the at least one processor, cause the apparatusfurther to: receive from the communication system values for first andsecond overload limits.
 7. The apparatus of claim 5, the at least onememory and the computer program code configured to, with the at leastone processor, cause the apparatus further to: indicate to surroundingbase stations slices supported by the apparatus.
 8. A method in acommunication system, comprising: obtaining information on slicessupported by surrounding base stations; obtaining information onoverloaded slices used by the surrounding base stations; receiving ameasurement report from a user terminal utilizing slices incommunication; determining based on the measurement report that ahandover is needed for the user terminal; selecting from the surroundingbase stations a target base station for handover based on themeasurement report, slices supported by the base stations and theinformation on overloaded slices, wherein if in the surrounding basestations more than one is acceptable based on the measurement report,select as a target base station the base station offering maximum numberof non-overloaded slices required by the user terminal.
 9. The method ofclaim 8, further comprising: receiving from surrounding base stationsindication of slices supported by the base stations that have loadexceeding a given first overload limit.
 10. The method of claim 9,further comprising: receiving from surrounding base stations indicationof slices that previously had load exceeding a given first overloadlimit have load reduced below a given second overload limit.
 11. Amethod in a communication system, comprising: determining the resourceavailability of supported slices; indicating to surrounding basestations if one or more slices have load exceeding a given firstoverload limit; and indicating to surrounding base stations if one ormore slices that previously had load exceeding a given overload limithas load fallen below a given second overload limit.
 12. The method ofclaim 11, further comprising: indicating to surrounding base stationssupported slices.
 13. A computer program embodied on a non-transitorycomputer-readable medium, said computer program comprising instructionsfor causing an apparatus of a communication system to perform at leastthe following: obtaining information on slices supported by surroundingbase stations; obtaining information on overloaded slices used by thesurrounding base stations; receiving a measurement report from a userterminal utilizing slices in communication; determining based on themeasurement report that a handover is needed for the user terminal;selecting from the surrounding base stations a target base station forhandover based on the measurement report, slices supported by the basestations and the information on overloaded slices, wherein if in thesurrounding base stations more than one is acceptable based on themeasurement report, select as a target base station the base stationoffering maximum number of non-overloaded slices required by the userterminal.
 14. A computer program embodied on a non-transitorycomputer-readable medium, said computer program comprising instructionsfor causing an apparatus of a communication system to perform at leastthe following: determining the resource availability of supportedslices; indicating to surrounding base stations if one or more sliceshave load exceeding a given first overload limit; and indicating tosurrounding base stations if one or more slices that previously had loadexceeding a given overload limit has load fallen below a given secondoverload limit.